Fungicides application timing, sequencing, and tank mixing for controlling blight in chickpea
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Total crop losses can result from ascochyta blight on chickpea (caused by Ascochyta rabiei). A study was conducted to investigate effective fungicide application strategies in particular fungicide application timing as well as product choices, sequencing and mixtures for blight control. In addition, this study is expected to provide information on resistance management through fungicide rotations, mixtures or sequences. Fungicide trials were conducted in Saskatoon and Swift Current using Bravo 500, Quadris, Headline, BAS510 and Dithane in various sequences or tank mixes on cultivars Myles and CDC Yuma. Only Bravo 500 is registered on chickpea. Quadris had emergency registration in 2002. Applications were timed at the seedling stage, pre-flower, early-flower, late-flower and the podding stages. These results relate to the trial at Swift Current. Cultivar CDC Yuma developed higher infection levels than Myles. The level of disease control by each fungicide treatment was dependent on cultivar. The above average rainfall in Swift Current increased the level of blight severity and consequently it required several sprays especially on cultivar CDC Yuma to protect the crop. Cool wet weather towards the end of the season also delayed maturity and affected yield and seed quality. Disease severity was 97% and 82% in the untreated plots of CDC Yuma and Myles, respectively. In treated plots, it ranged from 13-50% in Myles and 15-96% in CDC Yuma. The yields varied from 434 to1956 kg/ha for CDC Yuma and 1430 to 2627 kg/ha for Myles. When spraying started before symptoms (per calender sprays with five applications), the high rate of Dithane at 2.44 kg a.i./ha reduced disease severity and increased yield more than the low rate of Dithane at 1.68kg a.i./ha. Sequencing Headline and Dithane in the per calender spray was better than per calender sprays with Dithane alone on both cultivars. However, per calender spray with a high rate of Dithane alone compared well with some treatments which included Headline or Quadris on Myles. Almost all other sequences were effective on Myles, but on CDC Yuma the most effective were those that included mostly Headline and in some cases Quadris. In general, at least three sprays to Myles and most treatments with at least four sprays to CDC Yuma reduced blight to less than 50% and also increased yields by up to 84% in Myles and up to 351% in CDC Yuma. The results suggest that there could be a range of different fungicides and sequences one might use to adequately protect chickpea, but this will depend on the registration of products other than Bravo 500.
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